The present invention relates to a semiconductor integrated circuit and more particularly to a semiconductor integrated circuit which is suitable for a circuit for pulse driving a load such as a class-D amplifier.
As is well known, a class-D amplifier serves to turn ON/OFF a load driving output transistor and to intermittently carry out a conduction to a load. In the intermittent conduction to the load, a current flowing to parasitic inductances provided on a power line or a grounding conductor of the class-D amplifier is drastically changed. Therefore, noise is generated on these parasitic inductances, resulting in a ringing which appears in an output signal of the class-D amplifier. Such a ringing causes a deterioration in reproducing quality of the class-D amplifier, and furthermore, causes damage to the load or the class-D amplifier. For this reason, it is desired to reduce the ringing. Patent Document 1 has proposed a technique for decreasing a time gradient of an output signal waveform of an output transistor. By an application of the technique of this type to the class-D amplifier, the time gradient of the output signal waveform is decreased so that a current flowing to an output transistor can be prevented from being changed suddenly. Thus, it is possible to reduce the ringing.
Patent Document 1: Japanese Patent No. 3152204
However, the technique disclosed in the Patent Document 1 serves to decrease the time gradient of the output signal waveform. For this reason, there is a problem in that an operating speed of the class-D amplifier is sacrificed by the application of the technique. This problem is common to a semiconductor integrated circuit required to drive a load at a high speed and demanded to reduce a ringing in an output signal in addition to the class-D amplifier.